Potassium channels play a crucial role in controlling the physiological function of excitable cells; thus modulation of these channels may provide novel mechanistic approaches to treat cell dysfunction. The structure and function of physiologically important potassium channels and relevant structure-activity relationship have been thoroughly reviewed [see, eg, Atwal, K. Medicinal Research Reviews 1992, 12, 569–591; Gopalakrishan, M. et al Drug Development Research 1993, 28, 95–127; Lawson, K. Pharmacol. Ther. 1996, 70, 39–63; Aguilar-Bryan, L. et al Physiol. Rev. 1998, 78, 227–245; Evans, J. M. et al Progress in Medicinal Chemistry, 31; Ellis, G. P.; Luscombe, D. K., Eds.; Elsevier Science B. V., 1994; 411–447; Garcia, M. L. et al Adv. Pharmacol. 1997, 39, 425–471; McDonough, S. et al Drug Development Research 1994, 33, 190–202]. By virtue of their ability to hyperpolarize cell membranes and prevent the influx of Ca2+ ions through voltage-gated Ca2+ channels, compounds having activity as potassium channel openers relax smooth muscle cells. Several potent potassium-channel openers such as pinacidil and cromakalim have been studied clinically as antihypertensive agents. It has been shown that the ATP-dependent potassium channel does exist in the bladder and that it can be activated by numerous antihypertensive potassium channel openers [see, eg, Bonev, A. D. et al Am. J. Physiol. 1993, 264 (cell physiol 33), C1190–C1200; Fujii, K. et al. Br. J. Pharmacol. 1990, 99, 779–785; Malmgren, A. et al J. Urol. 1990, 143, 828–834; and Grant, T. L. et al J. Pharmacol. Exp. Thera. 1991, 269(3) 1158–1164].
European Patent No. 718290-A1 discloses carboxyalkyl heterocyclic derivatives as aldose reductase inhibitors useful in treating diabetic complications. Among the disclosed compounds are 4,5-dioxo-1-thioxoimidazolidines of the following formula:
wherein:    R is hydrogen or lower alkyl of 1–3 carbon atoms;    n is an integer of 1–3; and    X is benzyl, benzothiazolylmethyl, or naphthyl methyl.
U.S. Pat. No. 5,312,919 discloses the preparation and use of merodantoin (1) as an anticancer and antiviral agent. This patent further discloses compounds of formula 2:
wherein:    R1 and R2 may be hydrogen, C1–C6 alkyl, or benzyl.
U.S. Pat. Nos. 4,084,001 and 4,152,453 disclose the use of compounds of the following formulas 1 and 2 as intermediates in the preparation of histamine blocking agents and as inhibitors of acid secretion respectively.
wherein:    R is alkyl; and    n is an integer of 1–6.
U.S. Pat. No. 3,461,133 discloses compounds of following formula as herbicides:
wherein:    R is alkyl of 1–12 carbon atoms, alkenyl, or alkynyl.
German Patent DE 3540919 discloses compounds of following formula as herbicidal synergists:
wherein:    R1 is hydrogen, alkyl; and    R2 is alkyl, phenyl, or phenylalkyl.
German Patent DD 154819 discloses methods for the preparation of compounds of following formula (1) from 4,5-di-imino compounds (2):

German Patent DD 219483 A1 discloses compounds of the following formula as antitubercular agents:
wherein:    R is aryl; and    n is an integer of 1–2.